Electronic wavelength marker system and method

• US 20060274798A1
• Filed: 04/14/2006
• Published: 12/07/2006
• Est. Priority Date: 04/19/2005
• Status: Abandoned Application

• Current Assignee: Newport Corporation (MKS Instruments Incorporated)
• Original Assignee: Bookham Incorporated (Oclaro (North America), Inc.)
• Inventors: Pieterse, Jan-Willem Jozef, Pritchett, Russ, Wang, Weizhi, Cordes, Andrew H., Abriam, Rosemary O.
• Application Number:
  US11/404,369
• Publication Number:
  US 20060274798A1
• Time in Patent Office: Days
• US Class Current: 372/38.10
• CPC Class Codes: H01S 5/06 Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
• CPC Class Codes: H01S 5/0617 using memorised or pre-programmed laser characteristics
• CPC Class Codes: H01S 5/0654 Single longitudinal mode emission
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/143 Littman-Metcalf configuration, e.g. laser - grating - mirror

Abstract

A system is provided for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light; a laser cavity includes an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium; a position sensor that senses position of the element; position signal circuitry that produces a position signal indicative of position of the element sensed by the position sensor; a storage medium storing at least one position signal corresponding to a respective predetermined position of the element; comparison circuitry for comparing the produced position signal with the at least one stored position signal and for producing a comparison result indicative of whether the element has reached to the predetermined position; marker signal circuitry providing an external wavelength marker signal when the comparison result indicates that the element has reached the respective predetermined position.

Claims

1. A system for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light comprising:

a laser cavity including an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium;

a position sensor that senses position of the element;

position signal circuitry that produces a position signal indicative of position of the element sensed by the position sensor;

a storage medium storing at least one position signal corresponding to a respective predetermined position of the element;

comparison circuitry for comparing the produced position signal with the at least one stored position signal and for producing a comparison result indicative of whether the element has reached to the predetermined position;

marker signal circuitry providing an external wavelength marker signal when the comparison result indicates that the element has reached the respective predetermined position.

2. The system of claim 1,

wherein the laser cavity includes an optical gain medium, a reflector and a dispersive element disposed in a Littman-Metcalf configuration in which the wavelength selective element includes the reflector or the dispersive element.

3. The system of claim 1,

wherein the laser cavity includes an optical gain medium and a dispersive element disposed in a Littrow configuration in which the wavelength selective element is the dispersive element.

4. The system of claim 1,

wherein the laser cavity includes an optical gain medium and a filter disposed in an optical cavity configuration in which the wavelength selective element includes the filter.

5. The system of claim 1,

wherein the position signal circuitry includes,

an encoder that produces an analog signal indicative of position of the element sensed by the position sensor;

and

interpolator circuitry that produces a digital signal from the produced analog signal; and

wherein the at least one stored position signal is a digital signal.

6. The system of claim 1,

wherein the position signal circuitry includes,

an encoder that produces quadrature signals indicative of position of the element sensed by the position sensor;

and

interpolator circuitry that a produces a digital signal from the produced quadrature signals; and

wherein the at least one stored position signal is a digital signal.

7. The system of claim 1,

wherein the position signal circuitry includes,

an encoder that produces an analog signal indicative of position of the element sensed by the position sensor;

and

an A/D converter that converts the produced analog signal to a digital signal representing a count value; and

wherein the at least one stored position signal is a digital count value that represents the predetermined position of the element.

8. The system of claim 1,

wherein the position sensor includes,

a reticle that changes position with the element such that position of the reticle is indicative of position of the element;

a light source disposed on one side of the reticle;

a light detector that is disposed on an opposite side of the reticle and that produces a light detector signal indicative of changes in light passing through the reticle with changes in positions of the reticle and the element;

wherein the position signal circuitry includes,

an encoder responsive to the light detector signal that produces quadrature signals indicative of position of the element; and

interpolator circuitry that converts the produced quadrature signals to a digital count value that represents position of the element; and

wherein the at least one stored position signal is a digital count value representing the predetermined position of the element.

9. The system of claim 1 wherein

the marker signal circuitry produces an external wavelength marker signal having a prescribed transition when the comparison result indicates that the element has reached the respective predetermined position.

10. The system of claim 1,

wherein the storage medium stores multiple position signals each corresponding to a different predetermined position of the element;

and further including;

selection circuitry for selecting a next at least one stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position corresponding to a previously selected predetermined position signal.

11. The system of claim 1 further including:

a processor that is coupled to provide to the storage medium multiple predetermined position signals each corresponding to a different predetermined position of the element;

wherein the storage medium stores the provided multiple position signals; and

further including;

selection circuitry for selecting a next stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position corresponding to a previously selected predetermined position signal.

12. The system of claim 1 further including:

an actuator for changing position of the wavelength selective element;

13. The system of claim 1 further including:

a processor that is coupled to provide control signals to the actuator so as to control changing of position of the wavelength selective element by the actuator and that is coupled to receive as feedback the produced position signals indicative of position of the element sensed by the position sensor and that is coupled to provide to the storage medium multiple predetermined position signals each corresponding to a different predetermined position of the element;

wherein the storage medium stores the provided multiple position signals; and

further including;

selection circuitry for selecting a next at least one stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position that corresponds to a previously selected predetermined position signal.

14. The system of claim 1 further including:

an actuator for changing position of the wavelength selective element;

a processor that is coupled to provide control signals to the actuator so as to control changing of position of the wavelength selective element by the actuator and that is coupled to receive as feedback the produced position signals indicative of position of the element sensed by the position sensor and that is coupled to provide to the storage medium multiple predetermined position signals each corresponding to a different predetermined position of the element and that provides a RAM address information signal;

wherein the storage medium includes a RAM that stores the provided multiple position signals; and

further including;

selection circuitry that is coupled to receive the RAM address information from the processor and that is coupled to receive the comparison result and that is coupled to provide to the RAM a signal that selects a next at least one stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position corresponding to a previously selected at least one stored predetermined position signal.

15. A system for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light comprising:

a laser cavity including an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium;

an actuator for changing position of the wavelength selective element;

a position sensor that senses position of the element;

position signal circuitry that produces a digital position signal indicative of position of the element sensed by the position sensor;

a storage medium that includes a RAM that stores multiple predetermined position signals each comprising a different digital value corresponding to a different predetermined position of the element;

a processor that is coupled to provide control signals to the actuator so as to control changing of position of the wavelength selective element by the actuator and that is coupled to receive as feedback the produced position signals indicative of position of the element sensed by the position sensor and that is coupled to provide to the storage medium the multiple predetermined position signals and that provides a RAM address information signal;

comparison circuitry for comparing the produced digital position signal with a selected stored digital position signal and for producing a comparison result indicative of whether the element has reached a predetermined position that corresponds to a previously selected predetermined position signal;

selection circuitry that is coupled to receive the RAM address information signal from the processor and that is coupled to receive the comparison result and that is coupled to provide a to the RAM an address signal that selects a next stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position that corresponds to a previously selected stored predetermined position signal; and

marker signal circuitry providing an external wavelength marker signal when the comparison result indicates that the element has reached the respective predetermined position.

16. The system of claim 15 wherein

the marker signal circuitry produces an external wavelength marker signal having a prescribed pulse state transition when the comparison result indicates that the element has reached the respective predetermined position.

17. A system for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light comprising:

a laser cavity including an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium;

an actuator for changing position of the wavelength selective element;

a position sensor that senses position of the element, wherein the position sensor includes,

a reticle that changes position with the element such that position of the reticle is indicative of position of the element;

a light source disposed on one side of the reticle;

a light detector that is disposed on an opposite side of the reticle and that produces a light detector signal indicative of changes in light passing through the reticle with changes in positions of the reticle and the element;

position signal circuitry that produces a position signal indicative of position of the element sensed by the position sensor, wherein the position signal circuitry includes,

an encoder responsive to the light detector signal that produces quadrature signals indicative of position of the element; and

interpolator circuitry that converts the produced quadrature signals to a digital count value that represents position of the element; and

a storage medium that includes a RAM that stores multiple predetermined position signals each comprising a different digital value corresponding to a different predetermined position of the element;

a processor that is coupled to provide control signals to the actuator so as to control changing of position of the wavelength selective element by the actuator and that is coupled to receive as feedback the produced position signals indicative of position of the element sensed by the position sensor and that is coupled to provide to the storage medium the multiple predetermined position signals and that provides a RAM address information signal;

comparison circuitry for comparing the produced digital position signal with a selected stored digital position signal and for producing a comparison result indicative of whether the element has reached a predetermined position that corresponds to a previously selected predetermined position signal;

selection circuitry that is coupled to receive the RAM address information signal from the processor and that is coupled to receive the comparison result and that is coupled to provide a to the RAM an address signal that selects a next stored position signal from among the multiple stored position signals when the comparison result indicates that the element has reached a predetermined position that corresponds to a previously selected stored predetermined position signal; and

marker signal circuitry providing an external wavelength signal when the comparison result indicates that the element has reached the respective predetermined position.

18. A system for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light comprising:

a laser cavity including an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium;

means for changing position of the wavelength selective element;

means for sensing position of the element;

means for producing a position signal indicative of position of the element sensed by the position sensor;

means for storing at least one position signal corresponding to a respective predetermined position of the element;

comparison means for comparing the produced position signal with the at least one stored position signal and for producing a comparison result indicative of whether the element has reached to the predetermined position; and

means for providing an external wavelength marker signal when the comparison result indicates that the element has reached the respective predetermined position.

19. A method of determining wavelength of a light produced by a wavelength tunable laser system that includes a laser cavity including an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium, the method comprising:

(A) storing in a storage medium a plurality of predetermined position signals each corresponding to a different predetermined position of the element;

(B) selecting a predetermined stored position signal that corresponds to a next predetermined position;

(C) changing the position of the element so as to change the wavelength of light emitted by the laser system;

(D) sensing position of the element as the element changes position;

(E) producing a position signal indicative of the sensed position of the element;

(F) comparing the produced position signal with the selected stored predetermined position signal;

(G) producing an external marker signal indicative of the wavelength of light emitted by the laser system when the comparison indicates that the element has reached a respective predetermined position that corresponds to the selected predetermined position signal.

20. The method of claim 19,

wherein step (C), changing the position of the element, includes continuously changing the position of the element (or laserlight??) over a prescribed range;

(H) selecting a different predetermined stored position signal that corresponds to a different predetermined position;

(I) repeating steps (D)-(H) during the step (C) of changing position of the element.

21. The method of claim 19 further including:

using the produced position signal by a processor as feedback to control position of the element.